DISPSTR SEXP

 Function
  Display string of text defined by SEXP or display a file if SEXP is
  "%filename" or execute a PPE if SEXP is "!filename"

 Syntax
  DISPSTR str

   str  - A string expression to display, or
          if valid %filename display contents of given filename, or
          if valid !PPE-filename execute the PPE file.

 Remarks
  This statement in intended to allow you to easily display a string to
  the user and provide some of the functionality of PCBTEXT.  If the
  string to display begins with a percent sign and is followed by a valid
  file name, then the file will be displayed to the caller instead of the
  string.  Alternately, the string could begin with an exclamation mark
  (and be followed by a legal filename) to run a PPE file.

 Examples
  STRING s
  INPUT "String",s
  DISPSTR s
  LET s = "Regular string"
  DISPSTR s
  DISPSTR "%C:\PCB\GEN\BRDM"
  DISPSTR "!"+PPEPATH()+"SUBSCR.PPE"